In recent years, there have been paid attention contribution sites established by users' contributions such as blogs, mini-blogs and word-of-mouth sites over Internet. In such a contribution site, users' contribution information is posted on Web pages such that other persons can browse the information. The user can freely originate information by use of the mechanism. However, information unsuitable for being posted is present in the contribution information. There has been conventionally proposed a technique for preventing improper information from being posted.
For example, Patent Document 1 describes therein a technique for determining whether to post contribution information based on a judge's determination result as to whether to permit or prohibit the posting, and for determining whether to keep posting the contribution information based on a determination result indicating posting prohibition by a viewer who views the posting-permitted contribution information.